The below described invention deals with novel perfluoroalkyl group containing surfactants. The importance of the surfactants resides in the fact that they act as wetting, emulsifying, solubilizing and/or dispersing agents. Although surfactants have been prepared from many classes of compounds, more recently surfactants containing perfluoro alkyl (R.sub.f) groups have been reported. R.sub.f -substituted surfactants are especially valuable because they are known to reduce the surface tension of liquids more than any other surfactant. For instance, in water, surface tension of less than 17 dynes/cm can be obtained with fluorinated surfactants, whereas the non-fluorinated hydrocarbon analogs reduce the surface tension of water only to about 30 dynes/cm. For this reason the fluorinated surfactants have found applications in such diverse areas as emulsion-polymerizations, self-polishing floor waxes, electro-plating, corrosion inhibitors, paints, and fire fighting compositions.
A variety of fluorinated, amphoteric and cationic surfactants have been disclosed in U.S. Pat. Nos. 2,764,602, 3,555,089 and 3,681,413 and in German Offenlegungschrift Nos. 2,120,868; 2,127,232; 2,165,057 and 2,315,326. Although the compounds of the present invention also contain R.sub.f groups, they are substantially different from the surfactants disclosed in the above listed patents.
Possible intermediates which can be used in preparing the surfactants of this invention are disclosed in U.S. Pat. No. 3,471,518 wherein the addition of R.sub.f -alkylenethiols to maleic acid and maleates is disclosed and U.S. Pat. No. 3,706,787 wherein the addition products of R.sub.f -thiols are dialkyl maleates and monoalkyl maleates are disclosed. German Offenlegungsschrift No. 2,219,642 discloses R.sub.f -alkylenethiol addition products with dialkyl amino-alkyl acrylates and methacrylates, which compounds are cationic surfactants and do not possess a 1,2-dicarboxylic moiety. While all fluorinated amphoteric surfactants of the prior art are synthesized by quaternization of an appropriate tertiary amine with an alkylating agent, such as lactones, sultones or halogenated acids, the amphoteric surfactants of this invention are prepared by a simple ring-opening reaction without the use of potentially carcinogenic alkylating agents. The surfactants of this invention are superior wetting agents, especially when used in combination with other fluorinated and nonfluorinated surfactants. Furthermore, they can be manufactured much more economically and safely.